The present invention concerns the manufacture of integrated circuit media of the contactless type such as electronic labels or cards known as “contactless” because of their ability to exchange information at a distance with a reader in accordance with a read mode or a write/read mode.
Such cards are notably identification badges, or smart cards with more extensive functions whose applications are currently multiplying. For example, in such an application known as “remote billing”, the card is debited whilst passing close to a terminal and can likewise be recharged at a distance. As a general rule, the data transmission is effected by radio frequency or microwave.
In a known method of manufacturing a contactless card, the so-called “co-lamination” technique is used. It consists here of disposing, between the platens of a press, a stack of thermoplastic sheets in the middle of which the electronic circuit for contactless transmission is positioned; and then welding the different thermoplastic sheets by pressure and raising the temperature. This method makes it possible to obtain a card in which all the electronics are embedded in the plastics material. However, because of the differences between the coefficients of expansion of the various materials used, the combined action of the pressure and temperature causes a residual deformation on the surface of the card. And the remedy for this deformation is a great burden in terms of production, since it consists of substantially extending the cycle times, notably the cooling. Another drawback of these cards is their mediocre ability to resist repeated bending stresses.
In the document EP-A-0 640 940 in the name of N.V. Nederlandsche Apparentfabriek NEDAP, a solution to this dual problem is proposed according to which an intermediate layer with a support function for the functional means of the card is interposed between two surface layers, each of the latter being fixed to the intermediate layer by a connecting layer with a lower softening temperature. This method has however the disadvantage of including a large number of steps and therefore being fairly complex to implement.